1. Field of the Invention
This invention relates generally to a tire manufacturing mold and the method of making the same, and more specifically to a tire manufacturing mold comprising a profile ring having an inner circumferential surface corresponding to the outer profile of a tire being molded, including at least the tread thereof, and a net ring having a faying surface for making contact with the inner circumferential surface of the profile ring and consisting of ribs and/or lugs for forming the grooves of the tire being molded; the net ring being disposed on the profile ring; gas vent members being provided on the profile ring and/or the net ring; and venting gaps being formed on the periphery of the gas vent members to form gas vent passages, and the method of making the same.
2. Description of the Prior Art
In general, a tire manufacturing mold has a construction that patterns corresponding the outer profile of a tire being molded, that is as illustrated in FIG. 1, a tread portion 1 corresponding to the tread surface of the tire, and a rib portion 2 corresponding to the grooves on the tire surface, are provided on the inside surface of the mold. It is well known that the pattern formed by the tread portion 1 and the rib portion 2 and dimensional accuracy dictate the sterring, travelling, road-holding and noise suppressing performances of the tire.
Conventional tires have heretofore been manufactured by integrally forming the tread portion 1 and the rib portion 2, or welding the rib portion 2 in advance on the inner circumferential surface constituting the tread portion 1 using various types of precision casting processes, including plaster mold casting, sand casting, ceramic casting, metal mold casting, or engraving, electric discharge machining and other machining processes. With these constructions, the entire mold has to be redesigned and manufactured afresh every time tire design is changed to improve the aforementioned tire performances. In addition, the need for enormous manhours to change tire design or rearrange tooling entails a substantial increase not only in manufacturing costs but also in manufacturing time.
Furthermore, a tire manufacturing mold has gas vent holes leading to the outside from the mold surface to discharge charge the gas entrapped within the mold during tire molding. During tire molding operations, however, rubber debris often enter the gas vent holes, causing unwanted small projections on the tire surface or the clogging of the gas vent holes. This results in defective tires due to deteriorated gas discharging function or poor tire surface quality.